The invention relates to clutches and, more particularly, to improved adjusting rings used in clutches.
In order to transmit drive from an engine-driven flywheel to an output shaft, many clutches utilize levers for selectively urging driving and driven disks into contact with one another. The levers have first ends pivoted on a release sleeve and second ends pivoted on a clutch cover which rotates with the flywheel. Intermediate the ends of each lever are abutment surfaces which urge a pressure plate against the discs to effect frictional coupling of the discs. As the discs wear, the clutch will begin to slip if the position of the levers is not adjusted to compensate for the wear.
The adjustment is commonly accomplished by an adjusting ring having an externally threaded surface which is threadably coupled to an internally threaded surface of the clutch cover. By rotating the adjusting ring so as to axially advance it with respect to the clutch cover and the drive train, the second ends of the levers may be advanced so as to maintain proper pressure between the abutting surfaces of the levers and the pressure plate.
When the clutch is disengaged, the clutch adjusting ring is subject to substantial vibrations from the engine, especially in heavy truck applications. These heavy vibrations cause significant wear on the adjusting ring, and may even cause the ring to jump its threads. This, in turn, results in a loss of clutch adjustment and typically requires replacement of the adjusting ring.
Devices and methods to compensate for thread wear are well known. In one method, a seal is placed by, or around, the circumference of the threads to retain them in their proper position. These seals, however, frequently create an excessive amount of friction in the clutch, often causing the clutch to seize. Alternatively, means for locking the adjusting ring to the clutch cover may be used. However, this results in the loss of clutch adjustment once the driving and driven disks begin to wear. Additional methods include splitting the adjusting ring, sizing it to compensate for the thread wear, and then welding it back together. The splitting method, however, often produces an out-of-round ring which causes vibration or even driveline damage and clutch failure under load.
Therefore, it would be advantageous to have an inexpensive and efficient method to secure the adjusting ring to the clutch cover to withstand the vibrations of the engine, reduce or eliminate threadwear, and preserve the ability of the ring to provide clutch adjustment.